Dopamine, released from terminals of nigrostriatal neurons, interact with receptors in the neostriatum and plays a central role in the regulation of motor function. Receptors for acetylcholine, norepinephrine and other putative neurotransmitters are also present. There appear to be multiple subtypes of alpha and beta-adrenergic, muscarinic cholinergic, and dopamine receptors in the basal ganglia. A method has recently been developed which permits the simultaneous determination of beta-1 and beta-2-adrenergic receptors in tissues which contain both receptor subtypes. This technique or other approaches will be used to study the effect of various physiological and pharmacological manipulations on the subtypes of the several neurotransmitter receptors present in the caudate. Emphasis will be on effects of psychoactive agents and of drugs which affect transmitter uptake and storage. The pharmacological specificity of dopamine receptors on parathyroid and pituitary cells will be studied as examples of receptors that are or are not coupled to adenylate cyclase. The pharmacological specificity of receptors in the caudate will be compared with those in the two types of cells. In addition to studying binding with radiolabelled agonists and antagonists the effects of receptor activation on adenylate cyclase activity, parathyroid hormone release and inhibition of prolactin release will be measured. In other experiments, ontogeny of receptors and their subtypes will be studied in the caudate. Effects of incubating neostriatal slices and cultured cells with agonists will also be looked for. The cellular localization of neurotransmitter receptors in the caudate will be determined using autoradiography and physical separations of neurons from glia.